FYI the so-called Bertrand Russell quotation is apparently in fact an expanded paraphrase of Carl Sagan, The Burden of Skepticism (1987):

Britain has produced a range of remarkably gifted multidisciplinary scientists and scholars who are sometimes described as polymaths. The group included, in recent times, Bertrand Russell, A. N. Whitehead, J. B. S. Haldane, J. D. Bernal, and Jacob Bronowski. Russell commented that the development of such gifted individuals required a childhood period in which there was little or no pressure for conformity, a time in which the child could develop and pursue his or her own interests no matter how unusual or bizarre.

Still earlier Sagan The Dragons of Eden: Speculations on the Evolution of Human Intelligence (1977), Chapter 8, 'The Future Evolution of the Brain'.